1. Field of the Invention
The invention relates to direct access storage files composed of co-rotating pliant disks which are stacked at intervals too narrow for transducing access and particularly to means for effecting separation of disks in such files for external transducing access.
2. Description of the Prior Art
Disclosures cross-referenced above indicate evolutionary development of direct access mass storage files of floppy disks stacked at close (inaccessible) intervals determined by ventilating spacers and confined between co-rotating inflexible end plates. The spacers and end plates permit limited displacements of the rotational orbits of the disk storage surfaces which are useful to widen otherwise inaccessible (address) spaces in the stack sufficiently to allow unobstructed insertion of an externally transported head. The space to be widened can be selected on a random access basis.
Upon completion of transducing operation the head is withdrawn from the selected space and positioned externally for insertion into another selected address space.
Hitherto the separation displacement of the disks has been instigated by application of external force at the outer edges of disks facing the selected space. In earliest arrangements force would be applied continuously to maintain the separation. In a later arrangement (cross-reference 2 above) force applied transiently at the periphery of the stack would trigger a stable self-sustaining displacement of the disk orbits, due to ventilation conditioning of the stack to a state of bistable displacement equilibrium.
One problem with "external actuation" is that since the disks are not peripherally restrained the rotational orbits of individual storage surfaces may vary dynamically, thereby adding a factor of uncertainty to the procedure for locating the address at which to apply the force which instigates separation. Also, since the means employed to apply external force must occupy external space it is likely to increase the aggregate size of the storage system apparatus.
U.S. Pat. No. 2,960,340 (Seidel) discloses internal separation of stacked rigid disks by a co-rotating "actuator" device which translates axially relative to the disks. All of the disks are shifted vertically and the actuator is moved to a selected position where it expands outwardly into the stack to act as a stop. The stack is then released to permit all disks between the actuator and the lowest disk to fall by gravity onto a co-rotating turntable. A head is maneuvered into the space vacated by the dropped portion of the stack for transducing operation.
U.S. Pat. No. 3,130,393 (Gutterman) discloses external division of slidable disks in a piston configuration by pressure applied peripherally at a selected stack position.